An existing double-glass module uses tempered glass as a backplane, where a front surface uses EVA or PVB with a high UV transmittance, and a back surface uses a white EVA or PVB layer. The above double-glass module has following defects.
First, the back of the double-glass module uses airtight and waterproof glass, which can prevent water vapor from entering the module. However, a gap between edges of two pieces of glass is still a weak point, and water vapor can still enter the module by passing through an encapsulation film. Because of an airtight effect of glass, it is difficult for the water vapor to spread out. At the action of ultraviolet light, a small acetic acid molecule produced when an EVA encapsulation film is degraded can still erode a cell, and reduce a service life of the module. If the module is PVB encapsulated, because PVB has high water absorption, the problem is more severe.
Second, with the using of the white EVA or PVB layer in the back surface, a problem is that the white part may spread to the front surface of the cell after a long time of use and, thus, may block the cell, and cause a hot spot, affecting module efficiency.
Third, potential risks exist when edges of the module have no frame, because edges and corners are the most fragile parts of tempered glass. If improperly protected, the module is very easily cracked.